The present invention relates to air-heating gas burners, and particularly to a burner for burning a mixture of gaseous fuel and process air to heat the air for use in industrial applications. More particularly, the present invention relates to a line burner assembly including a fuel manifold and mixing plates mounted on the fuel manifold and formed to include apertures through which process air passes to mix with fuel discharged from the fuel manifold to produce a flame between the mixing plates.
Line burner assemblies are able to burn a mixture including a gaseous fuel and air to produce a flame. Line burners are disclosed in U.S. Pat. Nos. 3,297,259; 4,869,665; and 5,131,836, which patents are hereby incorporated by reference herein. The disclosures in U.S. Pat. Nos. 3,051,464; 3,178,161; and 4,573,907 are also hereby incorporated by reference herein.
It is known to provide elongated line burners which are formed to include a plurality of gaseous fuel openings and a plurality of air openings along the length of the burner. Such line burners are known as “nozzle mix” line burners. Examples of nozzle mix line burners are shown in U.S. Pat. Nos. 4,340,180 and 4,403,947, which patents are hereby incorporated by reference herein.
It is also known to supply a premixed gaseous fuel and combustion air mixture to a manifold of a line burner and ignite the mixture to produce a flame. Examples of “premix” line burners are shown in U.S. Pat. Nos. Re. 25,626; 3,178,161; 3,297,259; 4,573,907; and 4,869,665, which patents are hereby incorporated by reference herein.
Air-heating gas burners are well-suited to warm or temper incoming air into buildings to relieve the building heating plant of peak or extra loads. They can be used to create a warm air curtain on open docks and for process drying in industrial or agricultural applications.
Line burners are useful in various industrial applications where it is required to have a specific temperature distribution over a predetermined space or area. Examples of applications where line burners are used include graphics applications, incinerators, turbine boosters, and board dryers. In a graphics application, for example, premix line burners are used to generate hot air to dry ink or solvents from printing presses.
Process air is that air that is produced in a factory or industrial process and found to contain various inert matter entrained therein. It is desirable to dispose of this process air in an environmentally sound way to minimize unwanted discharge of inert matter into the environment. One way to dispose of many of the contaminants entrained in process air is to incinerate it by burning a mixture of gaseous fuel and process air in a line burner. For example, process air containing solvents emitted from a printing press can be introduced into a line burner and mixed with gaseous fuel to produce a flammable mixture. These entrained solvents are incinerated by the flame of the line burner as the process air passes through the mixing region of the line burner and the mixture of gaseous fuel and process air is ignited. It is important that this mixture contain enough oxygen to kindle or sustain a flame.
According to the present invention, a line burner includes a fuel manifold, a pair of perforated air-mixing plates coupled to the fuel manifold to define a fuel-air mixing region therebetween above the fuel manifold, and an unperforated air-deflector wing coupled to the top end of each air-mixing plate. The air-deflector wings are sized and arranged to stimulate recirculation of combustion products back into the primary reaction zone in the fuel-air mixing region to increase residence time of combustion products in a high-temperature region of the flame produced in the fuel-air mixing region.
In illustrative embodiments, the air-flow apertures formed in at least some of the air-mixing plates are sized, shaped, and spaced in a pattern selected to improve aeration in the fuel-air mixing region. In a section of the aeration pattern, the apertures are arranged in rows and columns. With respect to the rows, the apertures nearer the side edges of the air-mixing plates are larger than the apertures nearer the middle of the air-mixing plates. With respect to the columns, the apertures become smaller going down each column.
In other illustrative embodiments, a burner includes an elbow-shaped manifold and a wedge-shaped air-mixing plate mounted to the fuel manifold to accommodate a turn of the fuel manifold. The wedge-shaped air-mixing plate includes first and second side edges that diverge away from one another as they extend away from the fuel manifold.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments of the invention exemplifying the best mode of carrying out the invention as presently perceived.